and NeuAc. In Fig. , DPA revealed all monosaccharides analyzed. In this case, mobility and color could be used to distinguish specific sugars. Colors of different monosaccharides shown in Fig. varied from light blue to pink, gray, and purple. As shown in Fig. , color formation of chromatograms sprayed with Resorcinol was limited to shades of brown and purple. Also, the number of detectable sugars decreased considerably. Among the various sugars, Rib, dRib, Fru, and NeuAc were most intensively revealed by Resorcinol. However, Resorcinol did not reveal Glc, Fuc, GlcNH 2 , GlcNAc, KDN, KDO, or GlcA.
Figure displays chromatograms of chito-oligosaccharides, cello-oligosaccharides, neutral glycosphingolipids, and gangliosides revealed by DPA, Orcinol, and Resorcinol. Based on the results shown in Fig. , TLC plates were sprayed differentially to emphasize the advantages of DPA over Orcinol and Resorcinol. As shown in Fig. , DPA revealed both chito-and cello-oligosaccharides, with colors corresponding to those of GlcNAc and Glc, respectively (Fig. ). However, Orcinol only revealed cellooligosaccharides (Fig. ). Confirming the results shown in Fig. , Orcinol did not reveal those oligosaccharides containing GlcNAc (Fig. ). Figures and show the comparison of DPA and Resorcinol in revealing a number of representative glycosphingolipids. DPA revealed both neutral (blue) and sialic acid-containing (purple) glycosphingolipids (Fig. ). Thus, DPA can distinguish neutral glycosphingolipids from gangliosides. However, as shown in Fig. , Resorcinol only revealed gangliosides (sialic acid-glycosphingolipids). It should be noted that the color intensity of gangliosides revealed by Resorcinol was much lower than that of DPA.
Two classical spray reagents, anisaldehyde (6) and anthrone (7), are also widely used to reveal glycoconjugates on TLC plates. Like DPA, anisaldehyde and anthrone can reveal KDN and KDO. However, these two reagents cannot reveal GlcNAc and chito-oligosaccharides. Not only are the color intensities of the glycoconjugates revealed by these two reagents lower than those of DPA, but also the colors tend to fade after the plates are exposed to the air for more than 15 min.
Conclusion. The purpose of this note is to show the advantages of using DPA, a versatile, yet not widely used spray reagent, for revealing glycoconjugates on TLC plates. Compared to Resorcinol and Orcinol, DPA has proven to be a more sensitive reagent in revealing glycoconjugates containing neutral sugars, sialic acids, KDN, KDO, and hexosamines.